Optical tracking systems of the prior art particularly infrared tracking systems utilized to track moving objects have frequently utilized a single relatively large infrared detector element in conjunction with a suitable scanning device for scanning an image of the object across the infrared detector element. Tracking signals indicative of the displacement of the object from the axis of the scanning system have been developed by means of a reticule in optical alignment with the infrared detector element. The reticule modulates radiation from the object with a modulation pattern which indicates the direction of displacement of the object from the axis of the scanning system.
A problem arises in that the use of a single relatively large infrared detector introduces substantially more noise into the system than that introduced by a relatively small infrared detector element because, as is well known, the noise generated within an infrared detector element is proportional to the area of the detector element responsive to the incident radiation. The use of a multitude of relatively small infrared detector elements to counteract this problem of the single relatively large detector element may result in a far more complex scanning system in that the signals from each of the numerous detector elements must be separately received and correlated with the detector location and with the times of reception of these signals to extract information, such as the displacement of an object relative to the axis of the scanning system.